Can someone explain why these are used? Should I adopt one that is extremely obscure? What is the point of them?
(Obviously, mine is a complicated one to understand)
It's just a name Martin - or Brice (you may be French for all I know). Some folk are scared of the cast their own shadow makes on the floor, in case something about them is revealed - a public internet forum ditto. a username conceals things - a bit.
It's also one-upmanship to correspond with people in real name terms, whilst the majority remain in the demi-darkness of anonimity, with names like TimO, TimH, DesO, (although he has been injured and we haven't seen much of desolately...).
Besides, if I wrote Martin Flack on here, as a user name, the cops would find me, and I would have to 'fess up', but implicate Fingers Frank at the same time, which would do no good for the bonhomie of the Saturday morning drinks parties - in fact, it would be Frank incensed.
I'd go for 'obscure' if I were you, which, luckily, you're not.
Have fun!